1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and an apparatus for switching a frequency assignment in a wireless communication system.
2. Description of the Related Art
Not only can a mobile base station, configured by mounting a base station on a moving vehicle, provide services to mobile terminals when in motion, it can also perform the same function as that of fixed base stations when it is stationary.
A mobile base station may include a plurality of sector antennas and an omni antenna, and the following two types of antenna operating schemes may be used depending on the movement of the mobile base station. In other words, the mobile base station may use a sector antenna operating scheme, in which a plurality of sector antennas are used, for expansion of the cell capacity while it is stationary, whereas the mobile base station may use an omni antenna operating scheme, in which an omni antenna is used, to increase its mobility and stability while it is moving.
When using the sector antenna operating scheme, the mobile base station uses different Frequency Assignments (FAs) for different sectors of its cell(s). Accordingly, the mobile base station may perform the same operation as when a plurality of base stations are used.
When using the omni antenna operating scheme, the mobile base station uses an FA only for one sector of its cell. Therefore, when the mobile base station moves while in the stationary state, some of a plurality of FAs in use may not be used.
While the mobile base station is moving, a wireless environment between base stations is dynamically changed. Accordingly, the mobile base station needs to support the optimal wireless environment by adjusting its FA and transmission power depending on the changed wireless environment. In addition, the mobile base station needs to continuously provide seamless services to mobile terminals in its cell despite the change in the wireless environment.
Therefore, a need exists for a method and an apparatus for switching a frequency assignment in a wireless communication system.